Fail safe fluid power device

Abstract

A fluid power device such, for example, as one for opening and closing clam shell gates is operated by a ram under fluid pressure. A tank is provided for storing fluid under pressure and by a system of valving extension of the ram, as for a gate opening operation, is inhibited until enough fluid under pressure is stored in the tank to assure completion of reverse operation of the ram to close the gates.

Having described the invention, what is claimed as new in support of Letters Patent is as follows: 
     
       1. In a system for performing work by operation of a gas actuated ram comprising a cylinder and a piston therein forming in said cylinder a forward chamber and a reverse chamber wherein said reverse chamber has a reverse exhaust means at a pressure exceeding ambient pressure, and wherein said piston is movable between full forward and reverse positions, said system comprising an outside pressure connection adapted to provide a source of gas at forward operating pressure and an exhaust, a gas storage container means of capacity at least equal to the capacity of the reverse chamber with the piston at said full reverse position, said container means including a first gas passage means forming a connection between said container means and said outside pressure connection, operating valve means including a pressure diverting portion and a pressure exchange portion, gas passage means interconnecting said operating valve means with said outside pressure connection and said container means, said operating valve means having one adjustment wherein said pressure diverting portion is in a position blocking gas under pressure from said outside pressure connection to said forward chamber, sequence valve means interconnected with said container means and with said operating valve means, said sequence valve means having a first automatic adjustment at pressures less than said forward operating pressure operative to set said operating valve means at said one adjustment whereby to inhibit passage of gas by said operating valve means to said forward chamber, said sequence valve means having a second automatic adjustment when said container means is at said forward operating pressure, said operating valve means having another adjustment in response to said second automatic adjustment of the sequence valve means wherein said pressure exchange portion is part of an interconnection from said forward chamber through said outside pressure connection to said source and wherein said reverse chamber has a connection to said reverse exhaust means, at least a part of said operating valve means upon disconnection of said source from said outside pressure connection serving as an exhaust passage from said forward chamber, a reverse gas connection between said container means and said reverse chamber, said reverse gas connection being operative to pass gas under pressure to said reverse chamber whereby to reverse action of said ram when at least said part of said operating valve means is serving as an exhaust passage. 
     
     
       2. A system as in claim 1 wherein said sequence valve means includes our unloading vent operative to prevent overloading said system with fluid pressure. 
     
     
       3. A system as in claim 1 wherein the source of gas at forward operating pressure is air and there is a selector valve unit in communication with said operating valve means and said outside pressure connection whereby to communicate with said source, said operating valve means including a pilot operated valve unit which includes said pressure diverting portion, said pilot operated valve unit being responsive to said sequence valve means when at said forward operating pressure, said pilot operated valve unit having one position wherein passage of air from the selector valve unit to the forward chamber is blocked and the forward chamber is connected directly to exhaust and another position wherein air is passed to the forward chamber. 
     
     
       4. A system as in claim 1 wherein said reverse gas connection between the container and the reverse chamber contains said reverse exhaust means set at a pressure less than said forward operating pressure and a pressure regulator set at a pressure less than the setting of said reverse exhaust means. 
     
     
       5. A system as in claim 1 wherein the sequence valve means is connected directly to the container means and there is a pilot gas pressure line from said sequence valve means to said operating valve means. 
     
     
       6. A system as in claim 1 wherein there is a constantly open restricted vent connected to said sequence valve means. 
     
     
       7. A system as in claim 4 wherein the pressure regulator is set at a pressure substantially less than the forward operating pressure. 
     
     
       8. A system as in claim 1 wherein there is a selector valve unit in communication with said outside pressure connection, said pressure exchange and said pressure diverting portions of said operating valve means being responsive to said sequence valve means when at said forward operating pressure, said operating valve means including a gas line to said forward chamber, said part of said operating valve means comprising a quick exhaust valve unit in said gas line. 
     
     
       9. A system as in claim 1 wherein said outside pressure connection is constantly open and the pressure passed to said reverse chamber is less than the pressure at said source.